title: Fluorescence quenching of the phycobilisome terminal emitter LCM from the cyanobacterium Synechocystis sp. PCC 6803 detected in vivo and in vitro.
abstract: The fluorescence emission of the phycobilisome (PBS) core-membrane linker protein (L(CM)) can be directly quenched by photoactivated orange carotenoid protein (OCP) at room temperature both in vitro and in vivo, which suggests the crucial role of the OCP-L(CM) interaction in non-photochemical quenching (NPQ) of cyanobacteria. This implication was further supported (i) by low-temperature (77K) fluorescence emission and excitation measurements which showed a specific quenching of the corresponding long-wavelength fluorescence bands which belong to the PBS terminal emitters in the presence of photoactivated OCP, (ii) by systematic investigation of the fluorescence quenching and recovery in wild type and L(CM)-less cells of the model cyanobacterium Synechocystis sp. PCC 6803, and (iii) by the impact of dephosphorylation of isolated PBS on the quenching. The OCP binding site within the PBS and the most probable geometrical arrangement of the OCP-allophycocyanin (APC) complex was determined in silico using the crystal structures of OCP and APC. Geometrically modeled attachment of OCP to the PBS core is not at variance with the OCP-L(CM) interaction. It was concluded that besides being a very central element in the PBS to reaction center excitation energy transfer and PBS assembly, L(CM) also has an essential role in the photoprotective light adaptation processes of cyanobacteria.
authors.affiliation: AN Bakh Institute of Biochemistry, Russian Academy of Sciences, 119071 Moscow, Russia. stadnichuk@mail.ru
authors.forename: Igor N
authors.initials: IN
authors.lastname: Stadnichuk
authors.forename: Mikhail F
authors.initials: MF
authors.lastname: Yanyushin
authors.forename: Gábor
authors.initials: G
authors.lastname: Bernát
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Zlenko
authors.forename: Pavel M
authors.initials: PM
authors.lastname: Krasilnikov
authors.forename: Evgeny P
authors.initials: EP
authors.lastname: Lukashev
authors.forename: Evgeny G
authors.initials: EG
authors.lastname: Maksimov
authors.forename: Vladimir Z
authors.initials: VZ
authors.lastname: Paschenko
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D005453:Fluorescence; D008958:Models, Molecular; D045524:Phycobilisomes / Q000737:chemistry* / Q000378:metabolism; D046939:Synechocystis / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D045524:Phycobilisomes; C109473:orange carotenoid protein, Synechocystis
keywords: Allophycocyanin; Fluorescence; L(CM)-polypeptide; Orange carotenoid protein; Phycobilisome(s); Quenching